1. Field of the Invention
This invention pertains to the field of pollution control. More specifically, it pertains to processes for controlling algal and bacterial formations in aqueous bodies and, at the same time, for treating the dissolved water hardness and changing it into a form that permits removal by filtration. This invention finds specific application in controlling algal and bacterial growth and reducing calcium content in public and private swimming pools.
2. Description of the Prior Art
Algal and bacterial pollution are born of microscopic organisms. These organisms are carried in the air, on the skin of humans and animals and are found in virtually all bodies of liquid. Sunlight operates to catalyze the growth of algae and bacteria through cellular multiplication.
Calcium is found in virtually all bodies of water. It is dissolved by the action of rain on calcium-containing rock and carried by creeks and rivers, where more is dissolved from calcium-containing bedrock, into reservoirs, lakes and oceans. Where water undergoes extraction or biological control processes, such as in treatments to alter the growth of algal and bacterial growth, dissolved calcium tends to come out of solution and inhibit or spoil the treatment.
In aqueous bodies, the combination of sunlight and certain chemicals cause significant growth of algae and bacteria through photosynthesis. Fertilizer nitrates carried in water through run-off from farm fields and gardens make their way into creeks, reservoirs and rivers from which drinking water is obtained. Process foods contain nitrates and other chemicals that pass unchanged through digestive systems and sewage treatment systems to ultimately find their way back to drinking water reservoirs. Direct sunlight and that filtered through the clouds, in the presence of these chemicals, promote tremendous growth of algae and bacteria present in the water that ultimately impart undesirable taste in the water, and noxious fumes deteriorate and damage water purification systems and, in some cases, bind and clog filters and other cleansing medium.
Depollution of aqueous bodies has been generally a war of chemicals. Chemicals are added to deter further growth of algae and bacteria; however, these chemicals are as foreign to the human body as are the algae and bacteria and often cause deleterious affects to general health. While some chemicals have been proven exceptionally efficacious in stopping and even reversing the growth of algae and bacteria, these chemicals impart their own brand of noxious taste and odors to the water so that the final result is a less invasive water but just as obnoxious as it was when it contained the algae and bacteria.
Specifically, in aqueous bodies like swimming pools, constant exposure to sunlight maximizes growth of the minute quantities of algae and bacteria found therein. Even on overcast days, the light is sufficient to bring about grown of these minute particles carried into the water by wind, rain and on the swimmer's body and swim suit.
Conventional methods of maintaining low levels of pollution in swimming pools is to pour large quantities of aqueous solutions of chlorine-bearing compounds and oxygen-bearing compounds into the water to kill the algae and bacteria and then filter the dead material from the water. However, these chemicals degrade with time and exposure to light and must be replaced on a periodic basis to maintain the potential to kill newly introduced algae and bacteria. Not only are these chemicals expensive bust they pose substantial hazards to handlers. Filling a pool with hazardous chemicals of this type poses danger to not only the person adding the materials to the pool but to those who use the pool after the addition of the materials. Over-treatment is difficult to perceive visually and can lead to skin rashes, eye infections and worse diseases for those who use the pool after the over-treatment.
Recently, advances have been found in pollution control using spark and energy discharges between electrodes, see U.S. Pat. No. 3,402,120. Alternating electrical current has been found useful in controlling algal and bacterial growth in aqueous solutions with no harmful residual effects produced by the electrical current itself. These treatments, however, require the pre-addition of electrolyte compounds to the aqueous bodies and swimming pools to enhance the effect of the electrical energy, see U.S. Pat. No. 3,192,146. Sodium chloride is a common compound added to water preparatory to exposing the water to electrical discharge to control pollution, see U.S. Pat. No. 3,458,414. The deleterious effects of the sodium ion on the body are widely known and are sought to be avoided by many people, especially those with heart disease. Other treatments involving electricity and hypochlorite salts are also known to be efficacious, see U.S. Pat. No. 3,344,035; however, those salts may be deleterious to one's health.
In all of these prior art treatments, calcium dissolved in the body of water to be treated has tended to foul the reactions and interfere with the processes. Calcium tends to be at a saturation level because of the water's constant exposure to calcium-bearing materials such as rock and concrete. As soon as chemical alteration is undertaken, calcium begins to come out of solution as solid material, coating electrodes, plating filters and otherwise decreasing the effectiveness of the processes.
Silver has been found useful to kill bacteria when combined in filters through which the bacteria-laden water is passed. These filters, however, clog with use and require replacement. Thus, the silver is lost with the discarded filter and the cost of such a treatment is prohibitive. In other developments, silver ions in concentrations of three parts per billion, have been found to maintain concentrations of bacteria at acceptable levels. The addition of calcium hypochlorite as a supplement is needed along with a silver concentration and this compound also poses certain health risks in addition to becoming an adverse party by coating electrodes and damaging the electrolysis program. In addition, wide-spread use of silver in large bodies of water can be a cost problem.
A method has been found to use one inert electrode and one active electrode for controlling pollution in aqueous bodies, see U.S. Pat. No. 3,752,747. The active electrode is one that, upon being exposed to an electric potential, will introduce metallic ions into the aqueous body; an inert electrode will not introducing metallic ions into the body. Copper ions have been found to be very toxic to a wide range or algae and bacteria. In the aforesaid patent, one active electrode of copper and one inactive electrode is placed in spaced-apart relation in the aqueous body and an electrolytic potential applied therebetween where the discharge kills the algae formations and the copper ions kill the bacteria and the algae clinging to objects outside the electric field. The invention requires the use of one inert electrode so that when the concentration of copper ions is found to be of a sufficient amount to kill the bacteria and algae, the polarity is reversed between the electrodes to prevent further introduction of copper ions into the aqueous body.
A substantial problem has arisen from the use of this method, especially where the sides and bottom of the aqueous body are covered with aesthetically pleasing finishes. Copper ions stain light colored surfaces such as those found in the sides and bottoms of most swimming pools. While the copper is needed to toxify the algae and bacteria, its use in those concentrations causes so much staining that the pool owner would rather go back to using the chlorine-based chemicals and maintaining a goodlooking swimming pool than to keep re-painting or re-covering the stained sides of his swimming pool.
Recently, this inventor has discovered that the introduction of silver ions from silver/aluminum alloy electrodes under direct current conditions, where the polarity of the current is periodically reversed between them, provides efficacious control of algal and bacterial growth without the staining of the containment walls, such as the sides and bottoms of the swimming pool, as well as even utilization of the silver content in each electrode, reference my patent application Ser. No. 07/120,387; filing date 11/13/87; METHOD FOR CONTROLLING POLLUTION. In the practice of this invention, it has been noticed that, when direct current is used and either the polarity is held constant, reversed only during every other periodic application of power, or reversed at a low frequency, i.e., every five minutes or so, calcium begins to accumulate on the electrode in the form of a hard, impervious coating, being drawn to the electrode by the population of free electrons that gather at the negative polarity. The calcium thereafter remains on the electrode even after the polarity of the electrode has been reversed.
Such an accumulation gradually deteriorates the effectiveness of the electrode to pass current and free silver ions into the water. This results in the electrode needing periodic cleaning. Scraping the electrode with a knife or other sharp object, while being one method of cleaning, involves significant handling and possible gouging or damage to the electrode. Efficient cleaning of the electrode has been made possible by soaking it over night in a cleaning solution containing a deoxidizer/descaler such as #CC-3000, manufactured by Charles A Crosbie Laboratories, Inc., 1851 Randolph Street, Los Angeles, Calif. 90001.
This use of silver/aluminum alloy electrodes with either direct current or periodically reversed direct current is still quite useful because it not only controls algal and bacterial growth, but at the same time, removes calcium from the water resulting in a "softer" water that, as is generally known, is milder to the skin and promotes healing of skin maladies such as cuts, scrapes, burns and other irritations. However, it does have the concomitant problem of the need to use two sets of electrodes and to change them periodically by soaking the coated electrodes in the cleaning solution. This is not a process desired by all swimming pool owners.